The present invention generally relates to butterfly valves and, more particularly, to noise suppression wedges for butterfly outflow valves.
Many aircraft include a cabin pressure control system to control the cabin pressure. Cabin pressure control systems may have one or more outflow valves to assist in controlling cabin pressure by regulating air flow out of the cabin. One type of outflow valve that may be used in cabin pressure control systems is a butterfly valve.
A conventional butterfly valve 30 is depicted in FIG. 1. The prior art butterfly valve 30 comprises a disk 31 positioned within a bore 32 of a housing 33. The disk 31 can be rotated about an axis defined by a shaft 34 in order to control a flow of fluid, such as air (not shown) through the bore 32. The disk 31 may include a ring and seal assembly 35 to reduce leakage when the valve 30 is in a closed position. When the butterfly valve 30 is in an open position, the fluid flow may result in vibration or noise.
A butterfly valve with low noise has been disclosed in U.S. Pat. No. 6,338,468. The described butterfly valve includes an enlarged section of piping immediately downstream of the valve seat so as to control or suppress the noise. The enlarged section of piping has a diameter that is larger than the diameter of the valve disk. Although the described butterfly valve may reduce noise, it requires a section of downstream piping that is not included in some applications. Additionally, the butterfly valve of patent '468 may be most suitable for use with liquid flows, such as slurry.
A noise attenuating device for butterfly valves is disclosed in U.S. Pat. No. 5,881,995. The described butterfly valve includes a first series of elongated members extending from the upstream side of the disk and a second series of generally diametrically opposed elongated members extending from the downstream side of the disk. There may be three or more elongated members on each side of the disk. Each elongated member comprises a tab. One end of the tab is secured to the disk and the other end of the tab is bent to provide an angle between the tab and the surface of the disk. Although the tabs may reduce noise, each tab must be secured to the disk by means such as rivets or welding. The need to position and secure six of more tabs (three or more per side) to the disk increases manufacturing time.
As can be seen, there is a need for improved butterfly valves having noise suppression. Further, a noise suppression device is needed that does not require downstream piping. Additionally, there is a need for noise suppression devices that are easy to manufacture and install.